Countries of Potential Migrants to the United States

Based on the clues, can you guess these cities which start with each letter of the alphabet?

Name the countries that sent the most overnight visitors to the United States in 2023.

For each selected category, name any of the countries that ranks higher than the United States.

Which countries have received a Level 4 "Do Not Travel" advisory from the U.S. State Department since the beginning of 2023?